help me with basic rotating and moving problems

[zulo]

Hi

I have some problems with learning basic rotating, I have made a method
for moving a quad and rendering the quad, but when i rotate it always rotates the world, so it doesnt rotate around its own axis.

i want to rotate any object around its own axis without placing it exactly at 0,0

Is this the way its supposed to be? if i load a model then how can i know how to place it at exactly centered at 0,0? adn what if the model moves?

i really need help with this, please help me, i have looked in the opengl red book, and other tutorials + documents and forums and examples but i just cant get this rotating to work.

Here is the code so you can see what i do wrong..

What im trying to do in my render method is, calling firkant() that
moves and rotates and draws a quad on screen. This quad should rotate around its own z axis, but it wont do that unless i draw the quad exactly centered on 0,0

When the quad is drawn im drawing another quad that should not move...

import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.geom.AffineTransform;
import java.awt.image.AffineTransformOp;
import java.awt.image.BufferedImage;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.IntBuffer;

import org.lwjgl.Sys; 
import org.lwjgl.input.Keyboard; 
import org.lwjgl.openal.AL; 
import org.lwjgl.opengl.GL11; 
import org.lwjgl.opengl.Window;
 
/** 
 * $Id: Game.java,v 1.3 2004/05/05 14:35:05 cix_foo Exp $ 
 * 
 * This is a <em>very basic</em> skeleton to init a game and run it. 
 * 
 * @author $Author: cix_foo $ 
 * @version $Revision: 1.3 $ 
 */ 
public class Game { 
  
 /** Game title */ 
 public static final String GAME_TITLE = "My Game"; 
  
 /** Desired frame time */ 
 private static final int FRAMERATE = 60; 
  
 /** Exit the game */ 
 private static boolean finished;

private static boolean leftpressed =false;

private static boolean rightpressed =false;

private static float rotated = 0.0f;

private static float rtri = 0;

private static float rquad = 0;

private static int firkantz = 0;

  
 /** My texture */
 //private static int texture;
  
 /** 
  * No constructor needed - this class is static 
  */ 
 private Game() {} 
  
 /** 
  * Application init 
  * @param args Commandline args 
  */ 
 public static void main(String[] args) { 
  try { 
   init(); 
   run(); 
  } catch (Exception e) { 
   e.printStackTrace(System.err); 
   Sys.alert(GAME_TITLE, "An error occured and the game will exit."); 
  } finally { 
   cleanup(); 
  } 
 } 
  
 /** 
  * Initialise the game 
  * @throws Exception if init fails 
  */ 
 private static void init() throws Exception { 
  // Create a fullscreen window with 1:1 orthographic 2D projection, and with 
  // mouse, keyboard, and gamepad inputs. 
  Window.create(GAME_TITLE); 
   
  // Enable vsync if we can 
  Window.setVSyncEnabled(true); 
   
  // Start up the sound system 
  AL.create();
  
  // Enable texture mapping 
  //GL11.glEnable(GL11.GL_TEXTURE_2D);
  
  // TODO: Load in your textures etc here 
  //texture = loadTexture("data/nehe.png");
 } 
  
 /**
	 * Texture loading directly from LWJGL examples
	 */
	private final static int loadTexture(String path) {
		Image image = (new javax.swing.ImageIcon(path)).getImage();

		// Exctract The Image
		BufferedImage tex = new BufferedImage(image.getWidth(null), image.getHeight(null), BufferedImage.TYPE_3BYTE_BGR);
		Graphics2D g = (Graphics2D) tex.getGraphics();
		g.drawImage(image, null, null);
		g.dispose();

		// Flip Image
		AffineTransform tx = AffineTransform.getScaleInstance(1, -1);
		tx.translate(0, -image.getHeight(null));
		AffineTransformOp op = new AffineTransformOp(tx, AffineTransformOp.TYPE_NEAREST_NEIGHBOR);
		tex = op.filter(tex, null);

		// Put Image In Memory
		ByteBuffer scratch = ByteBuffer.allocateDirect(4 * tex.getWidth() * tex.getHeight());

		byte data[] = (byte[]) tex.getRaster().getDataElements(0, 0, tex.getWidth(), tex.getHeight(), null);
		scratch.clear();
		scratch.put(data);
		scratch.rewind();

		// Create A IntBuffer For Image Address In Memory   
		IntBuffer buf = ByteBuffer.allocateDirect(4).order(ByteOrder.nativeOrder()).asIntBuffer();
		GL11.glGenTextures(buf); // Create Texture In OpenGL   

		GL11.glBindTexture(GL11.GL_TEXTURE_2D, buf.get(0));
		// Typical Texture Generation Using Data From The Image

		// Linear Filtering
		GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_MIN_FILTER, GL11.GL_LINEAR);
		// Linear Filtering
		GL11.glTexParameteri(GL11.GL_TEXTURE_2D, GL11.GL_TEXTURE_MAG_FILTER, GL11.GL_LINEAR);
		// Generate The Texture
		GL11.glTexImage2D(GL11.GL_TEXTURE_2D, 0, GL11.GL_RGB, tex.getWidth(), tex.getHeight(), 0, GL11.GL_RGB, GL11.GL_UNSIGNED_BYTE, scratch);

		return buf.get(0); // Return Image Address In Memory
	}


/** 
  * Runs the game (the "main loop") 
  */ 
 private static void run() { 
  while (!finished) { 
   // Always call Window.update(), all the time 
   Window.update(); 
    
   if (Window.isCloseRequested()) { 
    // Check for O/S close requests 
    finished = true; 
   } else if (Window.isActive()) { 
    // The window is in the foreground, so we should play the game 
    logic(); 
    render(); 
    org.lwjgl.Display.sync(FRAMERATE); 
   } else { 
    // The window is not in the foreground, so we can allow other stuff to run and 
    // infrequently update 
    try { 
     Thread.sleep(100); 
    } catch (InterruptedException e) { 
    } 
    logic(); 
    if (Window.isVisible() || Window.isDirty()) { 
     // Only bother rendering if the window is visible or dirty 
     render(); 
    } 
   } 
  } 
 } 
  
 /** 
  * Do any game-specific cleanup 
  */ 
 private static void cleanup() { 
  // TODO: save anything you want to disk here 
 
  // Stop the sound 
  AL.destroy(); 
   
  // Close the window 
  Window.destroy(); 
 } 
  
 /** 
  * Do all calculations, handle input, etc. 
  */ 
 private static void logic() { 
  // Example input handler: we'll check for the ESC key and finish the game instantly when it's pressed 
  if (Keyboard.isKeyDown(Keyboard.KEY_ESCAPE)) { 
   finished = true; 
  } 
  if(Keyboard.isKeyDown(Keyboard.KEY_LEFT)){
  	leftpressed=true;
  }
  if(Keyboard.isKeyDown(Keyboard.KEY_RIGHT)){
  	rightpressed=true;
  }
  
  // TODO: all your game logic goes here. 
  if(rotated==360){
  	rotated=0;
  }
  else{
  	rotated++;firkantz++;
  }
  
  
  
  
 } 
  
 public static void firkant(){
 	 	
 	GL11.glMatrixMode(GL11.GL_MODELVIEW);
 	GL11.glLoadIdentity();
 	GL11.glPushMatrix();
 	
 	GL11.glLoadIdentity();
 	movefirkant();
 	renderfirkant();
	
	GL11.glPopMatrix();
 }
 public static void movefirkant(){
 	GL11.glTranslatef(400.0f,400.0f,0.0f);
 	GL11.glRotatef(firkantz,0.0f,0.0f,0.2f);
  }
 public static void renderfirkant(){
 	GL11.glBegin(GL11.GL_QUADS);
 	GL11.glVertex3f(0.0f, 0.0f, 0.0f);
 	GL11.glVertex3f(40.0f, 0.0f, 0.0f);
 	GL11.glVertex3f(40.0f, 40.0f, 0.0f);
 	GL11.glVertex3f(0.0f, 40.0f, 0.0f);
 	GL11.glEnd();
 }
 
 /** 
  * Render the current frame 
  */ 
 private static void render() { 
  
 	GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_STENCIL_BUFFER_BIT); 
  	
 	firkant();
 	
 	 	
 	GL11.glLoadIdentity();
 	GL11.glTranslatef(400.0f,400.0f,1.0f);
 	GL11.glRotatef(rtri,0.0f,0.0f,1.0f);
 	GL11.glBegin(GL11.GL_QUADS);
 		GL11.glVertex3f(-20.0f, -20.0f, 0.0f);
 		GL11.glVertex3f(20.0f, -20.0f, 0.0f);
 		GL11.glVertex3f(20.0f, 20.0f, 0.0f);
 		GL11.glVertex3f(-20.0f, 20.0f, 0.0f);
 	GL11.glEnd();
 	
 	
    

 } 
 
 
}

[Fool Running]

one of your problems (if not your only problem  :wink: ) is that you need to rotate the poly before you translate it in order to create the effect you are going for.

just change:

  GL11.glTranslatef(400.0f,400.0f,0.0f); 
   GL11.glRotatef(firkantz,0.0f,0.0f,0.2f);

in movefirkant() to:

  GL11.glRotatef(firkantz,0.0f,0.0f,0.2f); 
   GL11.glTranslatef(400.0f,400.0f,0.0f);

that will help alot  :lol: